Brake rebuild/bleed system problem

[Allen Henderson]

Brake dancers..

So, I totally rebuilt all calipers and MC on the '70T and all is back together. I've pumped a lot on the brake pedal but I don't have anything happening. That is the calipers are not gripping at all and fluid, if it is flowing in the system, isn't (yet) in the calipers or lines. The system started totally empty....

I offer the following possiblities

1. the two feed lines from the reservoir aren't getting brake fluid into the caliper because the lines aren't all the way in the grommets on top of the MC (this doesn't seem to be the case because when I open the lines at the MC fluid leaks out) But it is difficult to get those feed lines in...

2. The MC is assembled wrong (this is doubtful, I was really careful putting it back together and see the following..) and not producing pressure. This doesn't seem to be the case because I had my wife press on the peddle with me under the car, opening each line and fluid squirted out at the MC on both the front and rear section of the MC

3. I haven't pressed on the pedal enough or there is something really weird when you are working with a totally empty system.

Any ideas or suggestions? Thanks.

-Allen-

[Steve@Rennsport]

Allen,

IF you assembled the MC properly and IF there are no obstructions in the system that you don't knwo about, I'd kindly recommend that you pressure bleed it to get fluid where you need it,..

The Motive bleeders are really not expensive and IMHO, worth every dime,...

[Flieger]

You are sure that the center tunnel is not filling with fluid due to old hard lines leaking?

[Allen Henderson]

You are sure that the center tunnel is not filling with fluid due to old hard lines leaking?

Yes, not the problem. I've not blown out the lines, I'm going to do that now. Thanks for the suggestions.

-Allen-

[GWN7]

I just replaced all 4 rubber lines on the 69. Disconnected the hard lines at each caliper and at the master cyl and blew air thru them to remove any of the 15+ yr old fluid that was in them. Blew air thru the bleed screws to remove any in the calipers too. So I started off with a compleatly dry system.

With everything reassembled, leave the bleeders open and add the new fluid to the MC.....let gravity do some of the work for you and wait till the new fluid starts to come out of the bleeders, then shut them. Start bleeding from the shortest line, Left Front then do Right Front. With the rears the line is equal lenght so it dosen't matter which you do first. We had to do each line 5-6 times to ensure that there was no air in them, but ended up with good brakes. Keep topping up the MC

[lwalwa]

Did you put the calipers on the wrong side? I put 2 gallons through mine with a pressure bleeder before discovering what the PO had done. The brake pedal would go to the floor.

Larry

'71E Targa

[Allen Henderson]

Did you put the calipers on the wrong side? I put 2 gallons through mine with a pressure bleeder before discovering what the PO had done. The brake pedal would go to the floor.

Larry

'71E Targa

No, I'm thinking I need to look at my old rubber lines, I didn't replace them. I'm now guessing the fluid gets to them and then when the peddle is let up, they push the fluid back and it never gets beyond the beginning of the rubber lines....

-Allen-

[sithot]

I had some issues getting the seals on the calipers to "release" (open). The pedal to get firm but as soon as you left the car they drew back and I had no brakes.
The fix was to take the pads out and let the pistons extend thereby stretching the seals. They were pushed back in and the bleeding went off without a hitch.
It's also nice to pre-bleed the master cylinder. I do this on motorcycles and it saves time. It is amazing how much air is in a new system.

Tom

[GWN7]

No, I'm thinking I need to look at my old rubber lines, I didn't replace them. I'm now guessing the fluid gets to them and then when the peddle is let up, they push the fluid back and it never gets beyond the beginning of the rubber lines....

-Allen-

With mine it was the rubber lines that were the problem. They looked good and when we were pushing the car around (pre-running) the brakes worked fine. It wasn't untill the car was running and we did a panic stop to test them they developed problems. The LR one would lock up and not realise untill it was bleed down.

We figured the interior of the line had ballooned and would let fluid thru to engage the brakes, but would not let them realise untill bleed off at the bleeder.

$60 worth of new lines from Pelican solved the problem.

[edmayo]

The first thing you should check is the clearance for the master cylinder push rod since you had the master cylinder out. With the floorboard removed push the brake pedal down slightly then release it. Put your hand on the master cylinder push rod, can you feel a little play? now still with your hand on the push rod start to slowly push the brake pedal down, can you feel the slack go away in the pushrod or is it always the same, which means you have no clearance and the piston in the master cylinder isn't coming back far enough to open the relief port. There should be about 1mm clearance in the push rod. IF, everything else is correct it all should work.